West Nile Is Less Prevalent In Florida

Somewhere out in the swampy muck near Lake Okeechobee, in the canals of suburbia and in the puddles in our yards, mosquitoes infected with West Nile virus are hunting for something to bite.

Luckily, their numbers are quite low at the moment. And luckily, South Florida has been only brushed by the infectious invader that has spread throughout the state since July 2001.

While Louisiana scrambles to cope with a fatal outbreak, Florida is unexpectedly seeing less West Nile than it did a year ago.

No one really knows why. Maybe a few dry weeks in a row. Maybe strategic mosquito spraying. Maybe luck.

"I don't even have a guess," said Dr. James Cresanta, chief of disease prevention at the Broward County Health Department. "We'll just hold our breath."

The virus is here, for sure. Two chickens from regularly monitored "sentinel" flocks near Lake Okeechobee tested positive in Palm Beach County, along with a wild peacock near West Palm Beach and a horse in Miami-Dade County. Some mosquitoes tested in the region carried the virus.

So far, not a single human has been infected in Florida, vs. 12 last year.

"We're feeling pretty good about things at this point," said Dr. Bill Tynan, deputy state epidemiologist. "We might have expected more."

The mosquito-borne virus took only two years to spread to Florida since it first appeared in the U.S. in New York City in summer 1999.

The virus lives in birds, horses and other animals, and is spread to humans by mosquito bites. West Nile at its most severe can cause a fatal swelling of the brain and nervous system, but most people who get the virus fight it off with little effect. Fewer than 1 percent of infected people become seriously ill, mostly the elderly, young children and those with weakened immune systems.

In three years, the virus has struck 237 Americans and killed 22, including 88 sick and four dead this year. It has now spread across the Mississippi River into 34 states.

On Monday, the director of the U.S. Centers for Disease Control and Prevention, Dr. Julie Gerberding, said it's unlikely scientists can eradicate the virus in this country.

Scientists suggest viewing West Nile like its cousin, St. Louis encephalitis, as a fact of life.

"I really wouldn't worry about it that much," said Gary Goode, an environmental analyst for the Palm Beach County mosquito control division.

"People should look at it like lightning. If you have a thunderstorm outside, you go inside. If you're outside and getting chewed up by mosquitoes, go in the house."

South Florida's hordes of biters have greatly diminished over the past few weeks of dry weather after shooting way up during the big rains of July. Regular spraying has knocked down the few hot spots, said Joe Marhefka, Broward County's mosquito control manager.

It may be that the dry weather has merely delayed West Nile from appearing. And it's possible that this year's pattern of dry, wet and now dry periods may let the virus build up in dormant mosquitoes, making the outbreak worse if it does appear after big rains, expert Goode said. It might be that the virus waxes and wanes normally from year to year.

No one is sure.

"This is still very new in the states," epidemiologist Tynan said. "We're not going to be very good about predicting things until a few years go by. We really don't completely understand the pattern as yet."

Bob LaMendola can be reached at blamendola@sun-sentinel.com or 954-356-4526.